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CCNA lab 40 of 46

Troubleshooting a switched network: VLANs to EtherChannel

A switched campus with router-on-a-stick was 'tidied up' overnight and now nothing works. Find seven faults across access ports, VLANs, trunks, the native VLAN, an EtherChannel, spanning tree and a router subinterface, using only show commands and logs.

Run this lab

It needs Lite: its 6 nodes are set to 6 vCPU and 6,144 MB in total. That fits the free demo too.

In your workspace: Shared, then CCNA 200-301 guided labs, then 40 - Troubleshooting a switched network - VLANs to EtherChannel

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Level
Advanced
Time
About 60 minutes
Nodes need
6 vCPU, 6,144 MB
Smallest plan
Lite

The scenario

Overnight, a contractor at Halcyon Travel "standardised" the switch configurations. This morning: PC1 (staff, VLAN 10) and PC2 (sales, VLAN 20) can't reach their gateways, the access switches can't be managed, the uplink EtherChannel has half its bandwidth, and DSW1 logs complaints about native VLANs. There are seven faults. Work from the hosts outwards, prove each fault with output before you change anything, and keep a fault log.

Design (how it should be):

ItemDesign
VLANs10 STAFF (ASW1, DSW1, R1), 20 SALES (ASW2, DSW1, R1), 99 MGMT (all switches, native on every trunk)
GatewaysR1 subinterfaces Gi0/0.10 / .20 / .99 (native) = 10.40.x.1
TrunksR1–DSW1 (10, 20, 99), DSW1–ASW1 Po1 (10, 99), DSW1–ASW2 (10, 20, 99), ASW1–ASW2 (10, 99); native VLAN 99 everywhere
EtherChannelPo1 between DSW1 Gi0/1–2 and ASW1 Gi0/1–2, LACP, both members bundled
Spanning treeRapid PVST+; DSW1 is root for every VLAN
ManagementDSW1 10.40.99.2, ASW1 .3, ASW2 .4
HostsPC1 10.40.10.10 on ASW1 Gi1/0; PC2 10.40.20.10 on ASW2 Gi1/0

What you’ll practise

  • Troubleshoot Layer 2 methodically from the host outwards
  • Diagnose wrong access VLANs, missing VLANs and pruned trunks
  • Diagnose a native VLAN mismatch and its spanning-tree side effects
  • Diagnose an EtherChannel member that won't bundle and a misplaced root bridge
  • Diagnose a router-on-a-stick encapsulation fault

The tasks

  1. Start at PC1
  2. Follow VLAN 10 to the router
  3. Start at PC2
  4. Check the gateway side
  5. Check spanning tree against the design
  6. Fix everything and prove it

The Lab Tasks pane has the scenario, these tasks, the checks to run, hints and the full solution.

Topology and devices

The network as it opens in EVE-NG, drawn from the lab’s own canvas, and the image each node runs.

Topology of Troubleshooting a switched network - VLANs to EtherChannel6 nodes, 7 links. Every link is listed as text below the diagram.R1DSW1ASW1ASW2PC1PC2Gi0/0Gi0/0Gi1/0eth0Gi1/0eth0Gi0/1Gi0/1Gi0/2Gi0/2Gi0/3Gi0/0Gi0/0Gi0/1
6 nodes, with the interface names each link uses. On a narrow screen, scroll the diagram sideways.
Every link, as text
  • R1 Gi0/0 to DSW1 Gi0/0
  • DSW1 Gi0/1 to ASW1 Gi0/1
  • DSW1 Gi0/2 to ASW1 Gi0/2
  • DSW1 Gi0/3 to ASW2 Gi0/0
  • ASW1 Gi0/0 to ASW2 Gi0/1
  • ASW1 Gi1/0 to PC1 eth0
  • ASW2 Gi1/0 to PC2 eth0
Nodes in Troubleshooting a switched network: VLANs to EtherChannel, with the image each runs and the vCPU and RAM it’s set to
NodeDeviceImage in Add NodeSet to
R1Cisco IOSvvios-adventerprisek9-m.SPA.159-3.M61 vCPU, 1,024 MB
DSW1Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 1,024 MB
ASW1Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 1,024 MB
ASW2Cisco IOSvL2viosl2-adventerprisek9-m.ssa.high_iron_202009291 vCPU, 1,024 MB
PC1VPCS hostBuilt in to EVE-NGCounted as 1 vCPU, 1,024 MB
PC2VPCS hostBuilt in to EVE-NGCounted as 1 vCPU, 1,024 MB

How to open this lab

  1. Sign in to your workspace at lab.cloudlabbox.com.

  2. In File Manager, open Shared, then the folder CCNA 200-301 guided labs.

  3. Open 40 - Troubleshooting a switched network - VLANs to EtherChannel and start its nodes, then open Lab Tasks for the scenario and the steps.

The lab is read-only. You can start the nodes and configure the devices, but changes to the topology can’t be saved. To change it, rebuild it in your own folder.

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CloudLabBox is independent of Cisco. The lab follows exam topics and isn’t vendor training material; vendor names identify the exams and the images in the workspace.